Add new storage.conf option "transient_store"

This just adds the support for setting and handling this key, it
doesn't really do anything yet.

Signed-off-by: Alexander Larsson <alexl@redhat.com>

storage.conf

@@ -32,6 +32,10 @@ graphroot = "/var/lib/containers/storage"
 #
 # rootless_storage_path = "$HOME/.local/share/containers/storage"
 
+# Transient store mode makes all container metadata be saved in temporary storage
+# (i.e. runroot above). This is faster, but doesn't persist across reboots.
+# transient_store = true
+
 [storage.options]
 # Storage options to be passed to underlying storage drivers
 

store.go

@@ -141,6 +141,7 @@ type Store interface {
 	// settings that were passed to GetStore() when the object was created.
 	RunRoot() string
 	GraphRoot() string
+	TransientStore() bool
 	GraphDriverName() string
 	GraphOptions() []string
 	PullOptions() map[string]string
@@ -594,6 +595,7 @@ type store struct {
 	containerStore  rwContainerStore
 	digestLockRoot  string
 	disableVolatile bool
+	transientStore  bool
 }
 
 // GetStore attempts to find an already-created Store object matching the
@@ -701,6 +703,7 @@ func GetStore(options types.StoreOptions) (Store, error) {
 		additionalGIDs:  nil,
 		usernsLock:      usernsLock,
 		disableVolatile: options.DisableVolatile,
+		transientStore:  options.TransientStore,
 		pullOptions:     options.PullOptions,
 	}
 	if err := s.load(); err != nil {
@@ -748,6 +751,10 @@ func (s *store) GraphRoot() string {
 	return s.graphRoot
 }
 
+func (s *store) TransientStore() bool {
+	return s.transientStore
+}
+
 func (s *store) GraphOptions() []string {
 	return s.graphOptions
 }

types/options.go

@@ -22,6 +22,7 @@ type TomlConfig struct {
 		RunRoot             string            `toml:"runroot,omitempty"`
 		GraphRoot           string            `toml:"graphroot,omitempty"`
 		RootlessStoragePath string            `toml:"rootless_storage_path,omitempty"`
+		TransientStore      bool              `toml:"transient_store,omitempty"`
 		Options             cfg.OptionsConfig `toml:"options,omitempty"`
 	} `toml:"storage"`
 }
@@ -234,6 +235,8 @@ type StoreOptions struct {
 	PullOptions map[string]string `toml:"pull_options"`
 	// DisableVolatile doesn't allow volatile mounts when it is set.
 	DisableVolatile bool `json:"disable-volatile,omitempty"`
+	// If transient, don't persist containers over boot (stores db in runroot)
+	TransientStore bool `json:"transient_store,omitempty"`
 }
 
 // isRootlessDriver returns true if the given storage driver is valid for containers running as non root
@@ -452,6 +455,7 @@ func ReloadConfigurationFile(configFile string, storeOptions *StoreOptions) erro
 	}
 
 	storeOptions.DisableVolatile = config.Storage.Options.DisableVolatile
+	storeOptions.TransientStore = config.Storage.TransientStore
 
 	storeOptions.GraphDriverOptions = append(storeOptions.GraphDriverOptions, cfg.GetGraphDriverOptions(storeOptions.GraphDriverName, config.Storage.Options)...)